The United States launched its joint maritime security initiative in the Gulf, with the support of Australia, the United Kingdom and Bahrain, as tensions with Iran continue to escalate.

The US says the initiative is charged with protecting merchant vessels around the Strait of Hormuz - through which a third of the world’s oil passes - following Iran's seizure of a British oil tanker in the Strait last month.

US sanctions networks that it says are tied to Iran's missile programme

US Defence Secretary Mark Esper told reporters at the Pentagon on Wednesday that the presence of the United States and its allies in the region has so far deterred Iran from further action.

"I'm not sure I'm ready to call the crisis over yet, but so far so good and we hope the trend lines continue," Esper said.

The US announced its decision to form the protective force in July, days after Iranian forces downed a US drone near the strait.

The US said at the time that the drone had been flying over international waters, while Iran insisted the aircraft was shot down over its territory.

Iran has also been blamed for attacks on six tankers in or near the strait, accusations it denies.

The US has been trying to recruit allies for its maritime security coalition for weeks, but only the UK, Australia and Bahrain have joined.

France has declined to take part, as has Germany, which fears being pulled into a war against Iran.

Earlier this month, Israeli media reported that Foreign Minister Yisrael Katz told colleagues on the Knesset's defence committee that Israel is assisting with the naval mission.

Iranian leaders have reacted strongly to media reports of Israeli involvement, including Iranian President Hassan Rouhani, who weighed in on 14 August, warning that the Israelis "better ensure the security of where they are".

The UK was the first to join the US in its maritime coalition, while Bahrain joined next, earlier this month. Last week, Australia announced its participation.

Australia has sent a warship, surveillance aircraft and an unknown number of troops to assist, while the UK has sent at least two warships. It was unclear what kind of assistance Bahrain will provide.